Fructofuranose phosphates have been shown to be important metabolic regulators particularly in carbohydrate metabolism. Scores of enzymes were shown to have allosteric sites for fructose 1,6- and 2,6-bisphosphates. This study deals with structural and enzymatic studies of these modulators and analogues thereof. Interest in this group of compounds was kindled by our discovery of the hypoglycemic effect of 2,5-anhydro-D-mannitol (2,5-AM) in normal and diabetic animals. Its active form was shown to be the 1,6-bisphosphate which activates phosphofructokinase and pyruvate kinase and simultaneously inhibits the gluconeogenic enzyme fructose 1,6-bisphosphatase. This discovery revealed a new group of hypoglycemic agents hitherto unstudied. The specific aims of this project can be summarized as follows: (1) To ascertain the 3D structure of the newly discovered modulator, fructose 2,6-bisphosphate and to identify its enzymatically active anomer. This structure will be elucidated by X-ray diffraction. Because the current method of its synthesis is crude, an unambiguous method for the synthesis of its alpha- and beta-anomers is proposed. moreover, a procedure for the preparation of stable and stereochemically locked analogues for these two forms of F(2,6)P2 is given. (2) In view of the elevation of the blood tactic acid levels observed as a side effect of the hypoglycemic action of 2,5-AM, two gluconeogenic enzymes, namely phosphoenolpyruvate carboxykinase and malate dehydrogenase will be investigated for sensitivity to inhibition by its bisphosphate. (3) Moreover, the synthesis and testing of several new furanose analogues are proposed in an effort to develop a compound with hypoglycemic action and with minimal or no hyperlactic acidemic effect. These compounds were designed carefully on the basis of exploiting the differences in the activity levels and in the stereospecificity of hexokinase and fructokinase in liver vis-a-vis extrahepatic tissues. The enzymatic mechanism of the active compounds will be investigated.